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Rewrite nested jar support code and remove Java 8 support

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Rewrite nested jar code to better align with the implementations
provided in Java 17. This update makes two fundamental changes to
the previous implementation:

- Resource cleanup is now handled using the `java.lang.ref.Cleaner`

- Jar URLs now use the form `jar:nested:/my.jar/!nested.jar!/entry`

Unlike the previous `jar🫙/my,jar!/nested.jar!/entry` URL format,
the new format is compatible with Java's default Jar URL handler.
Specifically, it now only uses a single `jar:` prefix and it no longer
includes multiple `!/` separators.

In addition to the changes above, many of the ancillary classes have
also been refactored and updated to create cleaner APIs.

Closes gh-37668
This commit is contained in:
Phillip Webb
2023-09-18 12:30:13 -07:00
parent 75ddb9fa47
commit 7ad4a9817d
161 changed files with 13905 additions and 9577 deletions
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12
spring-boot-project/spring-boot-docs/src/docs/asciidoc/executable-jar/jarfile-class.adoc
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@@ -1,7 +1,7 @@
[[appendix.executable-jar.jarfile-class]]
== Spring Boot's "`JarFile`" Class
The core class used to support loading nested jars is `org.springframework.boot.loader.jar.JarFile`.
It lets you load jar content from a standard jar file or from nested child jar data.
== Spring Boot's "`NestedJarFile`" Class
The core class used to support loading nested jars is `org.springframework.boot.loader.jar.NestedJarFile`.
It lets you load jar content from nested child jar data.
When first loaded, the location of each `JarEntry` is mapped to a physical file offset of the outer jar, as shown in the following example:
[indent=0]
@@ -28,5 +28,7 @@ We do not need to unpack the archive, and we do not need to read all entry data
[[appendix.executable-jar.jarfile-class.compatibility]]
=== Compatibility With the Standard Java "`JarFile`"
Spring Boot Loader strives to remain compatible with existing code and libraries.
`org.springframework.boot.loader.jar.JarFile` extends from `java.util.jar.JarFile` and should work as a drop-in replacement.
The `getURL()` method returns a `URL` that opens a connection compatible with `java.net.JarURLConnection` and can be used with Java's `URLClassLoader`.
`org.springframework.boot.loader.jar.NestedJarFile` extends from `java.util.jar.JarFile` and should work as a drop-in replacement.
Nested JAR URLs of the form `jar:nested:/path/myjar.jar/!BOOT-INF/lib/mylib.jar!/B.class` are supported and open a connection compatible with `java.net.JarURLConnection`.
These can be used with Java's `URLClassLoader`.

7
spring-boot-project/spring-boot-docs/src/docs/asciidoc/executable-jar/launching.adoc
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@@ -1,13 +1,14 @@
[[appendix.executable-jar.launching]]
== Launching Executable Jars
The `org.springframework.boot.loader.Launcher` class is a special bootstrap class that is used as an executable jar's main entry point.
It is the actual `Main-Class` in your jar file, and it is used to setup an appropriate `URLClassLoader` and ultimately call your `main()` method.
The `org.springframework.boot.loader.launch.Launcher` class is a special bootstrap class that is used as an executable jar's main entry point.
It is the actual `Main-Class` in your jar file, and it is used to setup an appropriate `ClassLoader` and ultimately call your `main()` method.
There are three launcher subclasses (`JarLauncher`, `WarLauncher`, and `PropertiesLauncher`).
Their purpose is to load resources (`.class` files and so on) from nested jar files or war files in directories (as opposed to those explicitly on the classpath).
In the case of `JarLauncher` and `WarLauncher`, the nested paths are fixed.
`JarLauncher` looks in `BOOT-INF/lib/`, and `WarLauncher` looks in `WEB-INF/lib/` and `WEB-INF/lib-provided/`.
You can add extra jars in those locations if you want more.
The `PropertiesLauncher` looks in `BOOT-INF/lib/` in your application archive by default.
You can add additional locations by setting an environment variable called `LOADER_PATH` or `loader.path` in `loader.properties` (which is a comma-separated list of directories, archives, or directories within archives).
@@ -30,7 +31,7 @@ For a war file, it would be as follows:
[indent=0]
----
Main-Class: org.springframework.boot.loader.WarLauncher
Main-Class: org.springframework.boot.loader.launch.WarLauncher
Start-Class: com.mycompany.project.MyApplication
----